1. Field of the Invention
The present invention relates to an improved apparatus for continuously electroplating on a single surface of running metal strip.
2. Description of the Prior Art
In a conventional apparatus for continuously electroplating on a single surface of running metal strip 2 as shown in FIGS. 1 and 2, anodes 3 each having a width substantially equal to that of the strip are supported in a tank 1 containing an electroplating bath of a plating solution by means of anode supports 12 so as to be suitably arranged in longitudinally spaced relation and facing the strip. The strip itself functions as a cathode due to its being energized by means of rolls 14. In such a bath, a portion of the current flows around the side edges of the strip to the upper surface thereof opposite to the surface of the strip to be plated, and this causes the formation of undesirable additional deposits, each having a width from 40 to 60mm, on the upper surface adjacent to the side edges. In order to eliminate such deposits, anodes have been employed each having a width substantially equal to the wiedth of the strip; in addition, electric insulator sheets (such as the two sheets 4a shown in FIG. 3) have been utilized which are placed in contacting relation with both side edges of the upper surface of the strip to prevent the plating solution from circulating thereover. The plating solution cannot, however, be completely prevented from circulating thereover by such measures; thus, undesirable deposits are inevitably formed in a width of about 15mm (this width exceeding the width of about 10mm which will not be tolerated by most consumers). Such deposits are, in sum, caused for the reasons which follow (realizing of course that the deposits will only form on the upper surface of the strip if the solution is in contact therewith). First of all, the level of the plating solution in the tank is conventionally far higher than the level of the pass-line of the running strip so that the surface of the strip which is not to be plated, i.e., the upper surface of the strip, is completely immersed in the solution. Further, the conventional discharge nozzle 9 for supplying the plating solution to the tank is conventionally disposed in a perpendicular fashion to the pass-line of the running strip and at the same level as that of the strip, such that the desired close protective contact between the electric insulator sheets 4a and the strip is interfered with by the fluid action of the incoming plating solution, and the solution circulation thereof over between the insulator sheets and the upper surface of the strip cannot thus be prevented. At the same time, it has not been thought possible to remove the plating solution which is in contact with the upper surface zones of the strip where the strip is not contacted with the electric insulator sheets.
Thus, it is a primary object of the present invention to provide an improved apparatus for continuously electroplatint on a single surface of a running metal strip and which can minimize the undesirable deposits on the surface of the strip which is not to be plated.